Dissociative and Associative Concerted Mechanism for Ammonia Synthesis over Co-Based Catalyst

• Published in: Journal of the American Chemical Society Vol. 143; no. 32; pp. 12857 - 12866
• Main Authors: Ye, Tian-Nan, Park, Sang-Won, Lu, Yangfan, Li, Jiang, Wu, Jiazhen, Sasase, Masato, Kitano, Masaaki, Hosono, Hideo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18.08.2021
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c06657

The current catalytic reaction mechanism for ammonia synthesis relies on either dissociative or associative routes, in which adsorbed N2 dissociates directly or is hydrogenated step-by-step until it is broken upon the release of NH3 through associative adsorption. Here, we propose a concerted mechanism of associative and dissociative routes for ammonia synthesis over a cobalt-loaded nitride catalyst. Isotope exchange experiments reveal that the adsorbed N2 can be activated on both Co metal and the nitride support, which leads to superior low-temperature catalytic performance. The cooperation of the surface low work function (2.6 eV) feature and the formation of surface nitrogen vacancies on the CeN support gives rise to a dual pathway for N2 activation with much reduced activation energy (45 kJ·mol–1) over that of Co-based catalysts reported so far, which results in efficient ammonia synthesis under mild conditions.